Peak sun hours in Washington (2026)
Washington averages 3.8 peak sun hours per day — 19% below the US average of 4.7. In practical terms, every 1 kW of solar there produces about 1,110 kWh of electricity a year.
Peak sun hours/day
3.8
Annual kWh per kW
1,110
vs US average
-19%
What this means for your system
To produce a given amount of electricity, you need fewer panels where there are more peak sun hours. At 3.8 hours, a typical home in Washington needs a system sized to its usage and local sun — see exact numbers on the Washington solar cost page or work it out with our sizing guide.
Peak sun hours by city in Washington
Sunlight varies within Washington. Here are city-level figures from multi-year irradiance data.
| City | Peak sun hours/day | Annual kWh per kW |
|---|---|---|
| Seattle | 3.44 | 1,004 |
| Tri-Cities | 4.3 | 1,256 |
| Spokane | 4.05 | 1,183 |
| Tacoma | 3.55 | 1,037 |
| Vancouver | 3.69 | 1,077 |
Peak sun hours in Washington: FAQ
How many peak sun hours does Washington get?
Washington averages about 3.8 peak sun hours per day — 19% below the US average. That works out to roughly 1,110 kWh of electricity per year for every 1 kW of solar installed.
Is Washington good for solar based on sunlight?
Sunlight is only part of the picture. Washington's 3.8 peak sun hours are below average, so panels produce a little less, but your electricity rate and incentives matter just as much. See the full economics on our Washington solar cost page.